Zillow Mortgages tells you that you better make $225,000 a year if you want that million dollar home. Those mortgage payments will cost you $6,200 per month. That's assuming your rate is at 3.75% The app also lets you "shop rates," to fit your financial needs.When you're ready to refinance, Zillow Mortgages also offers that feature. The "refinance calculator" will help you figure out how much you need to save. Hopefully, you're not underwater. If you are, the app lets you review your options. This free app is compatible with iPhone, iPod touch, and iPad, but requires iOS 5.0 or later.